package homework.My21Point;

import java.util.Scanner;

public class magicNubser2 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        do {
            double v = scanner.nextDouble();
            if (v > 90) {
                System.out.println("a");
            }
            if (70 < v && 90 > v) {
                System.out.println("b");
            }
            if (60 < v && 70 > v) {
                System.out.println("c");
            }
            if (60 > v) {
                System.out.println("不及格");
            }
        }
        while (scanner.hasNextDouble());
}


        }